Method for producing hollow structural body

ABSTRACT

It is intended to provide a method of producing a hollow construct, which may be in various shapes such as a fiber or a film as well as in various sizes and has chemical resistance, made of a fluorinated hydrocarbon polymer, a fluorinated carbon polymer or a polymer carrying a nitrogen-containing group, a silicon-containing group, an oxygen-containing group, a phosphorus-containing group or a sulfur-containing group having been introduced into the above-described polymer; and a hollow construct obtained by this method.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.12/668,950, filed on Jan. 13, 2010 as the U.S. National Phase under 35.U.S.C. §371 of International Application PCT/JP2008/063691, filed Jul.30, 2008, which claims priority to Japanese Patent Application No.2007-199211, filed Jul. 31, 2007, which are hereby incorporated byreference in their entirety.

TECHNICAL FIELD

The present invention relates to a method for producing a hollowstructural body, and a hollow structural body obtained by the method,and more particularly to a method for producing a chemical-resistanthollow structural body having an opened hollow structure and made of afluorinated hydrocarbon polymer, a fluorocarbon polymer, or a polymerhaving a nitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer, and a hollowstructural body obtained by the method.

BACKGROUND ART

Heretofore, hollow structural bodies have been produced by variousmethods. For example, Patent Document 1 discloses a hollow ceramic fiberproduct and a method for producing the same. The Patent Documentdescribes that the hollow ceramic fiber product is made of a metal oxidehaving a thickness of 0.1 μm or more precipitated on a peripheralsurface of organic fibers from a solution containing a metal compoundserving as a precursor, and that holes corresponding to the shape of theorganic fibers are formed inside by removing the organic fibers.

However, the hollow ceramic fiber product is made of an inorganiccompound of ceramics and has poor lightweight feel compared with a fiberproduct made of an organic compound. Furthermore, since a metal oxidefilm is formed by immersing an organic fiber in a solution containing ametal compound serving as a precursor, it is difficult to control athickness of a coating film.

Also, there are high needs for a fiber having functionalities such aslightweight feel and heat retaining properties. Therefore, it is widelyused to produce various hollow synthetic fibers made of acryl,polyester, nylon, and the like.

Examples of the method for producing a hollow synthetic fiber include amethod in which a hollow structural body is formed during a spinningprocess using a spinneret, and a method in which a woven knit product isproduced using fibers composed of two components and the fiber of anyone of components is dissolved to form a hollow structural body. Theformer method is disclosed in Patent Documents 2 to 6. The latter methodis disclosed in Patent Document 7.

However, in the former method, regardless of wet spinning, dry spinningor melt spinning, a large-scale device is required. Since the productionmethod varied with a difference in a fiber material, production cost ishigh and skilled technique and knowledge are required, and also chemicalresistance is poor. Furthermore, the above production method is atechnique which can be applied only for fibrous products and it isdifficult to apply for various shapes and sizes, like a film. Since itis also a technique of forming a hollow structure during the productionprocess, it is difficult to form a hollow structure in commerciallyavailable products.

-   Patent Document 1: Japanese Unexamined Patent Publication (Kokai)    No. 2001-248024-   Patent Document 2: Japanese Unexamined Patent Publication (Kokai)    No. 9-78355-   Patent Document 3: Japanese Unexamined Patent Publication (Kokai)    No. 2003-105627-   Patent Document 4: Japanese Unexamined Patent Publication (Kokai)    No. 2005-256243-   Patent Document 5: Japanese Unexamined Patent Publication (Kokai)    No. 2006-45720-   Patent Document 6: Japanese Unexamined Patent Publication (Kokai)    No. 2006-9178-   Patent Document 7: Japanese Unexamined Patent Publication (Kokai)    No. 2007-016356

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In light, of the above problems, the present invention has been made,and an object thereof is to provide a method for producing a hollowstructural body which has various shapes and sizes, like a fiber and afilm, and is also made of a fluorinated hydrocarbon polymer, afluorocarbon polymer, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer, having a chemical resistance, and to provide a hollowstructural body obtained by the method.

Means for Solving the Problems

The present inventors have intensively studied about a method forproducing a hollow structural body and a hollow structural body obtainedby the method so as to solve the above conventional problems. As aresult, they have found that the above object can be achieved byadopting constitution shown below, and thus the present invention hasbeen completed.

That is, in order to solve the above-mentioned problems, the presentinvention relates to a method for producing a hollow structural body,which comprises a fluorination treatment step of bringing a structuralbody made of a hydrocarbon polymer, or a polymer having anitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the hydrocarbon polymer, intocontact with a treating gas containing fluorine under a predeterminedcondition to allow the treating gas to permeate the structural body fromthe outer surface toward the inside thereby fluorinating the structuralbody excluding the center portion thereof; and a removal step ofremoving the center portion in an unfluorinated state.

In the above method, according to the fluorination treatment step, thestructural body made of a hydrocarbon polymer, or a polymer having anitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the hydrocarbon polymer isbrought into contact with a treating gas containing fluorine, and thetreating gas is allowed to permeate the structural body toward theinside, thereby fluorinating the structural body excluding the centerportion thereof. Next, the center portion is removed to obtain an openedhollow structural body. The hollow structural body is made of afluorinated hydrocarbon polymer, a fluorocarbon polymer, or a polymerhaving a nitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer, and therefore isexcellent in chemical resistance against an acidic solution ofhydrofluoric acid or the like, a strong alkali solution of potassiumhydroxide or the like, and an organic solvent. Since an opened hollowstructure can be formed without restriction on the shape or size of thestructural body made of a polymer, increase in facility cost can besuppressed.

It is preferable that a portion of the structural body made of thepolymer is subjected to a step of masking for preventing fluorinationdue to the fluorination treatment, or a step of exposing the centerportion in an unfluorinated state in the structural body after beingsubjected to the fluorination treatment. Therefore, since the centerportion in an unfluorinated state can be exposed in the structural bodyafter being subjected to the fluorination treatment, the center portioncan be easily removed.

It is preferable that the removal step is a step of dissolving andremoving the center portion by bringing a solvent, in which the polymershows solubility and a solvent temperature is within a range from 0 to250° C., into contact with the exposed portion of the center portion. Byusing a solvent in which the polymer shows solubility, only the centerportion made of a hydrocarbon polymer or the like is dissolved andremoved, leaving only the portion made of a fluorinated hydrocarbonpolymer, a fluorocarbon polymer, or the like. Thus, the opened hollowstructural body can be obtained.

It is preferable that the removal step is conducted while heating at atemperature within a range from 50 to 400° C. under an inactive gasatmosphere. Therefore, the unfluorinated center portion can be removedby firing. As a result, even when a hydrocarbon polymer excellent inchemical resistance, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer is used, or a solvent in which the polymer shows solubilitycannot be found out, only the center portion can be removed and thus anopened hollow structural body can be obtained.

It is preferable that a pre-treatment step of heating the structuralbody made of the polymer under an inactive gas atmosphere under apredetermined condition is conducted before the fluorination treatmentstep. Therefore, since an inhibition component, which inhibits theprogress of a fluorination treatment, such as moisture or a volatilecomponent contained in the structural body made of a polymer can beremoved in advance, a hollow structural body excellent in chemicalresistance can be obtained.

It is preferable that a post-treatment step of heating the structuralbody immediately after the fluorination treatment step under apredetermined condition is conducted. Thereby, the unreacted treatinggas remained in the structural body, and impurities such as hydrogenfluoride generated during the reaction and adsorbed on a surface of thestructural body can be removed. By heating, fluorination can be allowedto proceed further inside the structural body and thus mechanicalstrength can be further improved.

It is preferred to use, as the treating gas, at least any one gasselected from the group consisting of hydrogen fluoride (HF), fluorine(F₂), chlorine trifluoride (ClF₃), sulfur tetrafluoride (SF₄), borontrifluoride (BF), nitrogen trifluoride (NF₃) and carbonyl fluoride(COF₂), or one prepared by diluting the gas with an inactive gas.

It is preferable that the hydrocarbon polymer is an olefin polymer, acyclic olefin polymer, an aromatic unsaturated hydrocarbon polymer, apolar group-containing polymer, or a copolymer containing two or morethese polymers.

Furthermore, in order to solve the above-mentioned problems, the presentinvention relates to a hollow structural body obtained by the method forproducing a hollow structural body, which has an opened follow structureand is made of a fluorinated hydrocarbon polymer, a fluorocarbonpolymer, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer.

With the above constitution, the hollow structural body is made of afluorinated hydrocarbon polymer, a fluorocarbon polymer, or a polymerhaving a nitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer, and therefore isexcellent in chemical resistance against an acidic solution ofhydrofluoric acid or the like, a strong alkali solution of potassiumhydroxide or the like, and an organic solvent. Furthermore, the hollowstructural body of the present invention may have an opened hollowstructural body including a hollow portion communicating with outside,and has the high degree of freedom with respect to the shape and size.Therefore, the hollow structural body of the present invention can beapplied for fibrous and film-shaped products.

It is preferable that a hollow ratio is within a range from 0, to 99%.The “hollow ratio” means a ratio of the cross-sectional area of thehollow portion to the entire cross-sectional area including the hollowportion in the cross section of the hollow structural body.

Effect of the Invention

According to the present invention, a hollow structural body excellentin chemical resistance and a method for producing the same can beprovided easily with low cost without restriction on the shape and size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing one example of a reactor used in theproduction of a hollow structural body according to the embodiment ofthe present invention.

FIG. 2 is a SEM micrograph of a hollow structural body in presentExample 1.

FIG. 3 is an XPS spectrum of a hollow structural body in present Example1.

FIG. 4 is a SEM micrograph of a hollow structural body in presentExample 2.

FIG. 5 is an XPS spectrum of a hollow structural body in present Example2.

FIG. 6 is a SEM micrograph of a hollow structural body in presentExample 3.

FIG. 7 is an XPS spectrum of a hollow structural body in present Example3.

FIG. 8( a) is a SEM micrograph of a hollow structural body in presentExample 4 and FIG. 8( b) is a comparative SEM micrograph of a hollowstructural body in present Example 1.

FIG. 9 is a SEM micrograph of a hollow structural body in presentExample 5.

FIG. 10 is an XPS spectrum of a hollow structural body in presentExample 5.

EXPLANATION OF REFERENCES

-   1: Inactive gas feed line-   2: Fluorination gas feed line-   3: Reaction vessel-   4: Structural body-   5: Heater-   6: Exhaust line-   7: Vacuum line

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained with reference tothe accompanying drawings. Provided that, unnecessary portions forexplanation are omitted, and some portions are illustrated on anenlarged or reduced scale for the easier understanding of explanation.

The hollow structural body according to the present embodiment is aresin integral molded article which has an opened hollow structure andis made of a fluorinated hydrocarbon polymer, a fluorocarbon polymer, ora polymer having a nitrogen-containing group, a silicon-containinggroup, an oxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer. The shape of thehollow structural body is not particularly limited to a fibrous shapeand may be a film. In the case of a fibrous hollow structural body, thehollow portion is continuously provided in the fiber axial direction.

When the hollow structural body according to the present embodiment isin the form of a fiber, the thickness thereof is not particularlylimited and can be appropriately set, if necessary. For example, in thecase of a hollow structural body having a diameter of 100 μm, thethickness thereof is preferably within a range from 0.1 to 9.9 μm, andmore preferably from 1.0 to 9.0 μm. When the thickness is less than 0.1μm, it may be impossible to sufficiently exert a function as the hollowstructural body. In contrast, when the thickness exceeds 9.9 μm, thetorsion may occur as a result of deterioration of shape retention forthe hollow structural body.

When the hollow structural body according to the present embodiment isin the form of a film, the thickness thereof is not particularly limitedand can be appropriately set, if necessary. For example, in the case ofthe hollow structural body in which the total thickness of a film is 100μm, the thickness of the coating film is preferably within a range from0.1 to 9.9 μm, and more preferably from 1.0 to 9.0μ. When the thicknessis less than 0.1 μm, it may be impossible to sufficiently exert afunction as the hollow structural body. In contrast, when the thicknessexceeds 9.9 μm, shape retention for the hollow structural body maydeteriorate.

The fluorinated hydrocarbon polymer means a polymer in which a portionof a hydrocarbon polymer described hereinafter is fluorinated, and thefluorocarbon polymer means a polymer in which a hydrocarbon polymer iscompletely fluorinated.

The hollow structural body according to the present embodiment is madeof a fluorinated hydrocarbon polymer, a fluorocarbon polymer, or apolymer having a nitrogen-containing group, a silicon-containing group,an oxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer, and thereforeexhibits excellent chemical resistance against an acidic solution ofhydrofluoric acid, sulfuric acid, hydrochloric acid, nitric acid,hydrogen peroxide water, or the like, or a mixed acid containing two ormore these acidic solutions. It also exhibits excellent chemicalresistance against a strong alkali solution of potassium hydroxide,sodium hydroxide, or the like. Furthermore, it exhibits excellentchemical resistance against an organic solvent such as an aromaticsolvent, a cyclic solvent or a chain solvent.

The hollow ratio of the hollow structural body is preferably within arange from 0.1 to 99%, and more preferably from 1 to 90%. When thehollow ratio is less than 0.1%, it may be impossible to sufficientlyexert a function as the hollow structural body. In contrast, when thehollow ratio exceeds 99%, the torsion may occur as a result ofdeterioration of shape retention for the hollow structural body.

Next, the method for producing a hollow structural body according to thepresent embodiment will be explained. In the production method, at leasta fluorination treatment step of a structural body made of a hydrocarbonpolymer, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer, and a removal step of removing the unfluorinated centerportion are conducted.

The hydrocarbon polymer is not particularly limited and includes, forexample, an olefin polymer, a cyclic olefin polymer, an aromaticunsaturated hydrocarbon polymer, a polar group-containing polymer, or acopolymer containing two or more these polymers. More specifically,examples of the olefin polymer include polyethylene, propylene,polybutene-1, an ethylene-propylene copolymer, an ethylene-butene-1copolymer, an ethylene-hexene-1 copolymer and a propylene-butene-1copolymer. Examples of the aromatic hydrocarbon polymer includepolystyrene and a styrene-divinylbenzene copolymer. Examples of thepolar group-containing polymer include polyvinyl chloride,polycarbonate, polymethyl methacrylate, polyethylene terephthalate,polyacrylonitrile, or a copolymer containing two or more these polymers.Examples of the cyclic olefin polymer include a norbornene polymer, adicyclopentadiene polymer, a tetracyclododecane polymer, anethyltetracyclododecene polymer, an ethylidenetetracyclododecenepolymer, a tertacyclo[7.4. 0.1^(10,13).0^(2,7)]trideca-2,4,6,11-tetraene polymer, a norbornene-based polymersuch as 1,4-methano-1,4,4a,9a-tetrahydrofluorene, a cyclobutene polymer,a cyclopentene polymer, a cyclohexene polymer, a3,4-dimethylcyclopentene polymer, a 3-methylcyclohexene polymer, a2-(2-methylbutyl)-1-cyclohexene polymer, a cyclooctene polymer, acycloheptene polymer, a cyclopentadiene polymer, a cyclohexadienepolymer, or a copolymer containing two or more these polymers. Also, acopolymer containing at least one monomer which composes the olefinpolymer, cyclic olefin polymer, aromatic hydrocarbon polymer and polargroup-containing polymer, for example, an ethylene-methyl methacrylatecopolymer, an ethylene-styrene copolymer and an ethylene-2-norbornenecopolymer are exemplified. Also, natural fibers such as rayon, cupra,wool, silk and cellulose are exemplified. Furthermore, synthetic fiberssuch as acryl, polyester, polyurethane and nylon are exemplified. Amongthese polymers, preferred are those which can be easily substituted withfluorocarbon by a fluorination treatment.

In the present invention, it is also possible to apply a polymer havinga nitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group for the hydrocarbon polymer. Thenitrogen-containing group is not particularly limited and includes, forexample, an alkylamino group such as an amino, methylamino,dimethylamine, diethylamino, dipropylamino, dibutylamino ordicyclohexylamino group, an arylamino group such as a phenylamino,diphenylamino, ditolylamino, dinaphthylamino or methylphenylamino group,or an alkylarylamino group. The silicon-containing group is notparticularly limited and includes, for example, a methylsilyl group, aphenylsilyl group, a dimethylsilyl group, a diethylsilyl group, adiphenylsilyl group, a trimethylsilyl group, a triethylsilyl group, atripropylsilyl group, a tricyclohexylsilyl group, a triphenylsilylgroup, a dimethylphenylsilyl group, a methyldiphenylsilyl group, atritolylsilyl group and a trinaphthylsilyl group. The oxygen-containinggroup is not particularly limited and includes, for example, an alkoxygroup such as a methoxy, ethoxy, propoxy or butoxy group, an allyloxygroup such as a phenoxy, methylphenoxy, dimethylphenoxy or naphthoxygroup, an arylalkoxy group such as a phenylmethoxy or phenylethoxygroup, and an ether group. The phosphorus-containing group is notparticularly limited and includes, for example, a dimethylphosphinogroup and a dipheylphosphino group. The sulfur-containing group is notparticularly limited and includes, for example, a thiol group, asulfonate group and a sulfinate group.

The structural body made of the hydrocarbon polymer, or a polymer havinga nitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer is preferablysubjected to a predetermined pre-treatment step in advance. Morespecifically, the structural body is preferably subjected to apre-treatment step of heating under an inactive gas atmosphere. Theinhibition component, which inhibits the progress of a fluorinationtreatment, such as moisture or a volatile component contained in thestructural body can be removed in advance by conducting thepre-treatment step. As a result, a hollow structural body having furtherimproved chemical resistance can be obtained.

The pre-treatment step is conducted, for example, by placing thestructural body 4 in a reaction vessel 3 and introducing the inactivegas into the structural body 4 through an inactive gas feed line 1 (seeFIG. 1). The inactive gas is not particularly limited as long as it isone other than a gas which reacts with the structural body therebyexerting adverse effects, or a gas containing impurities which exertsadverse effects. For example, dry air, nitrogen, argon, helium, neon,krypton and xenon can be used alone or in combination. There is noparticular limitation on purity of the inactive gas. However, thecontent of impurities which exerts adverse effects is preferably 100 ppmor less, more preferably 10 ppm or less, and particularly preferably 1ppm or less.

Depending on the structural body, moisture and oxygen among impuritiescontained in the inactive gas may serve as a factor which inhibitsconversion into fluorocarbon thereby decreasing the mechanical strengthof the hollow structural body. Therefore, the concentration of themoisture and oxygen existing in the inactive gas to be used ispreferably 100 ppm or less, more preferably 10 ppm or less, andparticularly preferably 1 ppm or less. As a matter of course, dry aircannot be used when oxygen exerts adverse effects.

The reaction vessel 3 is not particularly limited and those made ofstainless steel, aluminum or nickel can be used.

The structural body 4 is heated by a heater 5. The heating temperaturemay be appropriately set according to physical properties of ahydrocarbon polymer, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer and is usually within a range from 60 to 160° C., andpreferably from 60 to 120° C. The heating time may be appropriately setaccording to physical properties of the polymer and is usually within arange from 1 to 600 minutes, and preferably from 1 to 360 minutes. Thestructural body 4 is preferably heated while monitoring the moisturecontent using a dew-point meter.

Furthermore, the structural body 4 may be heated under reduced pressureand the pressure is not particularly limited, and is preferably 10 Pa orless, and preferably 1 Pa or less.

The fluorination treatment step is a step in which a structural bodymade of a hydrocarbon polymer, or a polymer having a nitrogen-containinggroup, a silicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer is brought into contact with a treating gas containingfluorine, and thus a portion other than the center portion of thestructural body is fluorinated. As the treating gas, at least any onegas selected from the group consisting of hydrogen fluoride (HF),fluorine (F₂), chlorine trifluoride (ClF), sulfur tetrafluoride (SF₄),boron trifluoride (BF₃), nitrogen trifluoride (NF₃) and carbonylfluoride (COF₂), or one prepared by diluting the gas with an inactivegas can be used. The inactive gas used for dilution is not particularlylimited as long as it is one other than a gas which reacts with thetreating gas thereby exerting adverse effects, and a gas which reactswith the structural body thereby exerting adverse effects or a gascontaining impurities which exerts adverse effects. For example, dryair, nitrogen, argon, helium, neon, krypton and xenon can be used aloneor in combination. There is no particular limitation on purity of theinactive gas. However, the content of impurities which exerts adverseeffects is preferably 100 ppm or less, more preferably 10 ppm or less,and particularly preferably 1 ppm or less.

The fluorination treatment is conducted, for example, in the followingmanner. First, a valve of the inactive gas feed line 1 shown in FIG. 1is closed, then a valve of a vacuum line 7 is opened and the reactionvessel 3 is under reduced pressure. The pressure is not particularlylimited and is preferably 10 Pa or less, and more preferably 1 Pa orless. If necessary, the inside of the reaction vessel 3 may bepre-heated or pre-cooled.

After the pressure was reduced to a predetermined pressure, the valve ofthe vacuum line 7 is closed, and then the valves of the inactive gasfeed line 1 and a fluorination gas feed line 2 are opened. Whereby, aninactive gas is mixed with a fluorination gas in the line and theresultant mixed gas is fed to the reaction vessel 3 as the treating gas.

There is no particular limitation on the concentration and flow rate ofthe fluorination gas. However, the reaction between the fluorination gasand a hydrocarbon polymer, or a polymer having a nitrogen-containinggroup, a silicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer may explosively occur at the initial stage. Therefore, it isimportant that the concentration and flow rate of the fluorination gasbe properly set at the initial stage of the reaction. That is, dependingon the progress of the reaction, the concentration and flow rate mayappropriately increase or decrease and the concentration of thefluorination gas can be usually set within a range from 0.001 to 100%.At the initial stage of the reaction, the concentration of thefluorination gas is preferably set within a range from 0.001 to 30%,more preferably from 0.001 to 20%, and particularly preferably from0.001 to 10%, so as to mildly conduct the reaction between the polymerand the fluorination gas.

The concentration of the fluorination gas in the treating gas can beadjusted depending on the flow rate of the gases to be fed trough theinactive gas feed line 1 and the fluorine gas feed line 2. Thefluorination gas may be continuously fed under normal pressure,increased pressure or reduced pressure, or enclosed under normalpressure, increased pressure or reduced pressure.

From a view point of mildly conducting the reaction between ahydrocarbon polymer, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer and the fluorination gas at the initial stage, thetemperature of the polymer is set at a low temperature at the initialstage of the reaction and then the temperature may be raisedcontinuously or intermittently depending on the progress of thereaction. Specifically, the reaction temperature is preferably within arange from −50 to 250° C., and more preferably from −20 to 200° C. Whenthe reaction temperature is lower than −50° C., the structural body madeof a polymer is not sufficiently fluorinated to obtain a hollowstructural body having a thin thickness and a low mechanical strength.In contrast, when the reaction temperature is higher than 250° C., ahollow structure may not be obtained since the structural body made of apolymer is completely fluorinated, including the center portion.

The time (reaction time) of the fluorination treatment is notparticularly limited and is usually within a range from 1 to 600minutes, preferably from 1 to 300 minutes, and still more preferablyfrom 1 to 150 minutes. When the reaction time is less than 1 minute, ahydrocarbon polymer, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer may not be sufficiently fluorinated to obtain a hollowstructural body having a thin thickness and a low mechanical strength.In contrast, when the reaction time exceeds 600 minutes, a hollowstructure may not be obtained since the structural body made of apolymer is completely fluorinated, including the center portion.

The thickness of the hollow structural body can be controlled byappropriately setting the concentration of the fluorination gas, thereaction temperature and the reaction time, if necessary. The thicknesscan be increased when each of these parameters is increased, while thethickness can be decreased when each of these parameters is decreased.

The treating gas is brought into contact with a hydrocarbon polymer, ora polymer having a nitrogen-containing group, a silicon-containinggroup, an oxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer and, after a lapseof a predetermined time, the valve of the fluorination gas feed line 2is closed and the inactive gas is continuously fed through the inactivegas feed line 1, and thus the treating gas within the reaction vessel 3is replaced by the only inactive gas.

Subsequently, the structural body after being subjected to thefluorination treatment is heated by using a heater (post-treatmentstep). This heat treatment enables the removal of the remainingfluorination gas not completely reacted with a hydrocarbon polymer, or apolymer having a nitrogen-containing group, a silicon-containing group,an oxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer in the structuralbody, and impurities generated during the reaction and adsorbed on thesurface of the structural body. The heat treatment also enables theprogress of fluorination to the inside of the structural body, and thusthe mechanical strength can be further increased. The heatingtemperature is preferably set to the temperature higher than thefluorination treatment temperature. The heating temperature may beappropriately set depending on physical properties of a fluorinatedhydrocarbon polymer, a fluorocarbon polymer, or a polymer having anitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer, and is preferablywithin a range from 50 to 250° C., and more preferably from 50 to 200°C. The reaction time is preferably from 1 to 600 minutes, and morepreferably from 1 to 360 minutes. When the reaction temperature is lowerthan 50° C. or the reaction time is less than 1 minute, the fluorinationgas or impurities may not be sufficiently removed. In contrast, when thereaction temperature is higher than 250° C. or the reaction time is morethan 600 minutes, there may arise such a problem that the mechanicalstrength of a fluorinated hydrocarbon polymer, a fluorocarbon polymer,or a polymer having a nitrogen-containing group, a silicon-containinggroup, an oxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer decreases.

After the fluorination treatment step, the structural body made of afluorinated hydrocarbon polymer, a fluorocarbon polymer, or a polymerhaving a nitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer is taken out fromthe reaction vessel 3. Next, when the center portion of the structuralbody in the unfluorinated state is not exposed, processing such ascutting of a portion of the structural body is conducted so as to exposethe center portion by the following reason that when the unfluorinatedunreacted center portion is not exposed outside, the center portioncannot be removed in a removal step described hereinafter. Before thefluorination treatment, a portion of the structural body made of ahydrocarbon polymer, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer may be subjected top masking in advance. In this case, amask is removed before the removal step described hereinafter. Themasking method includes, for example, a method of coating a portion, notto be reacted, with a surface protective material such as a maskingtape.

Next, the removal step of removing the center portion in theunfluorinated state is conducted. The removal step is conducted by amethod of immersing a structural body made of a fluorinated hydrocarbonpolymer, a fluorocarbon polymer, or a polymer having anitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer in a predeterminedsolvent. The solvent is not particularly limited and may beappropriately set depending on the kind of a hydrocarbon polymer, or apolymer having a nitrogen-containing group, a silicon-containing group,an oxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer. Specifically, anorganic solvent such as xylene is exemplified for polyethylene and apolypropylene polymer. Also, an organic solvent such as cyclohexane orcyclooctane is exemplified for a norbornene polymer.

In the step of immersing the polymer after being subjected to thefluorination treatment in a solvent to remove the center portion, thesolvent may be heated or the solvent may be heated under reflux byproviding with a reflux condenser. The step may be conducted underatmospheric pressure, increased pressure or reduced pressure. However,when the step is conducted under increased pressure, the unfluorinatedcenter portion can be dissolved and removed rapidly. The solventtemperature is not particularly limited and can be appropriately setdepending on a boiling point of an organic solvent to be used.Specifically, the solvent temperature is preferably within a range from0 to 250° C., and more preferably from 0 to 150° C. When the solventtemperature is lower than 0° C., it may become difficult to rapidlydissolve and remove the center portion. In contrast, when the solventtemperature is higher than 250° C., there arises a problem that afluorinated hydrocarbon polymer, a fluorocarbon polymer, or a polymerhaving a nitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer itself is dissolved.While the heating temperature is within a range from 60 to 160° C. inthe pre-treatment step of the structural body, the heating temperaturecan be increased to 250° C. in the present step. This means that heatresistance can be improved by the fluorination treatment of thestructural body. The immersion time can also be appropriately setdepending on the solubility of a hydrocarbon polymer, or a polymerhaving a nitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer, the shape and sizeof the structural body, and the kind of the solvent.

When a solvent in which the polymer shows solubility cannot be foundout, heating under an inactive gas atmosphere may also be conducted asthe removal step. The unfluorinated center portion can be removed due tomelting or firing also in this method. The mechanical strength of theportion converted into a fluorinated hydrocarbon polymer or afluorocarbon polymer as a result of the fluorination treatment can befurther increased.

The heating temperature can be appropriately set depending on physicalproperties of a hydrocarbon polymer, or a polymer having anitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer and the shape andsize of the structural body. Specifically, the heating temperature ispreferably from 50 to 400° C., and more preferably from 100 to 300° C.While the heating temperature is within a range from 60 to 160° C. inthe pre-treatment step of the structural body, the heating temperaturecan be increased to 400° C. in the present step. This means that heatresistance can be improved by the fluorination treatment of thestructural body. Also, the heating time can also be set by the reasonsimilar to the case of the heating temperature. Specifically, theheating time is preferably from 30 to 200 minutes. After removal of thecenter portion by heating, the hollow structural body is cooled to roomtemperature. This step may be conducted under atmospheric pressure,increased pressure or reduced pressure.

The inactive gas is not particularly limited as long as it is one otherthan a gas which reacts with the structural body thereby exertingadverse effects, or a gas containing impurities which exerts adverseeffects. For example, dry air, nitrogen, argon, helium, neon, kryptonand xenon can be used alone or in combination. Herein, the content ofimpurities which exerts adverse effects is preferably 100 ppm or less,more preferably 10 ppm or less, and particularly preferably 1 ppm orless.

According to the above method, a hollow structural body, which has anopened follow structure and is made of a fluorinated hydrocarbonpolymer, a fluorocarbon polymer, or a polymer having anitrogen-containing group, a silicon-containing group, anoxygen-containing group, a phosphorus-containing group or asulfur-containing group introduced into the polymer, can be obtained. Ahydrocarbon polymer, or a polymer having a nitrogen-containing group, asilicon-containing group, an oxygen-containing group, aphosphorus-containing group or a sulfur-containing group introduced intothe polymer according to the present embodiment can be formed into fiberto obtain a hollow fiber. A fiber structural body produced by using thehollow fiber as a raw material is excellent in lightweight propertiesand chemical resistance compared with a conventional one. The presenthollow structural body can also be applied for medical appliances suchas catheter.

EXAMPLES

Below, preferred examples of the present invention are explained indetail. However, materials, addition amounts, and the like described inthese examples are not intended to limit the scope of the presentinvention, and are only examples for explanation as long as there is nodescription of limitation in particular.

Example 1

As shown in FIG. 1, a fibrous structural body 4 made of a cyclic olefinpolymer (manufactured by ZEON CORPORATION under the trade name of ZEONOA1060) was charged into a reaction vessel 3 and a valve of a vacuum line7 was opened, and then evacuation was conducted until the pressure inthe reaction vessel 3 was reduced to 1 Pa or less.

Next, the valve of the vacuum line 7 was closed and a valve of aninactive gas feed line I was opened, and a nitrogen gas was introducedinto the reaction vessel 3. When the pressure in the reaction vessel 3showed an atmospheric pressure, a valve of an exhaust line 6 was openedand a heat treatment was conducted at a nitrogen flow rate of 1.5 L/minat 90° C. for 1 hour. A temperature rise rate was set at 2.0° C./min(pre-treatment step).

After a lapse of a predetermined time, the inside of the reaction vessel3 was cooled to 30° C. and the valves of the inactive gas feed line 1and the exhaust line 6 were closed, whereby, the inside of the reactionvessel 3 was brought into a closed state. Thereafter, the valve of thevacuum line 7 was opened and evacuation was conducted until the pressurein the reaction vessel 3 was reduced to 1 Pa or less.

Next, the valve of the vacuum line 7 was closed and the valves of theinactive gas feed line 1 and a fluorination gas feed line 2 weresimultaneously opened, and then a 5% fluorine gas diluted with anitrogen gas so as to achieve the concentration of a fluorine gas of 5%and a total flow rate of 100 cc/min was introduced into the reactionvessel 3 until the pressure reached an atmospheric pressure.

When the pressure showed the atmospheric pressure, the valves of theinactive gas feed line 1 and the fluorination gas feed line 2 weresimultaneously closed, whereby, the inside of the reaction vessel 3 wasbrought into a closed state, followed by retention for 1 hour(fluorination treatment step).

After a lapse of a predetermined time, using a heater 5, the structuralbody 4 was heated to 90° C. and, after reaching 90° C., the structuralbody was retained for 1 hour (fluorination treatment step). Atemperature rise rate was set at 0.1° C./min.

Next, the inside of the reaction vessel 3 was cooled to room temperatureand the valves of the inactive gas feed line 1 and the exhaust line 6were opened. After replacing the fluorine gas within the reaction vessel3 by a nitrogen gas, the valves of the inactive gas feed line 1 and theexhaust line 6 were closed, the valve of the vacuum line 7 was opened,and then evacuation was conducted until the pressure in the reactionvessel 3 was reduced to 1 Pa or less.

Next, the valve of the vacuum line 7 was closed and the valve of theinactive gas feed line 1 was opened, and a nitrogen gas was introducedinto the reaction vessel 3 at a flow rate of 1.5 L/min. When thepressure in the reaction vessel 3 showed the atmospheric pressure, thevalve of the exhaust line 6 was opened, followed by heating at atemperature rise rate of 2° C./min using the heater 5. After reaching95° C., the structural body was retained for 1 hour. After a lapse of apredetermined time, the inside of the reaction vessel was cooled to roomtemperature, and the structural body 4 was taken out (post-treatmentstep).

Subsequently, the structural body 4 was cut into pieces measuring 20mm×20 mm, followed by immersion in 50 g of cyclooctane (99.8%) at roomtemperature for 24 hours. Next, the structural body 4 was taken out,washed with isopropyl alcohol, dried at 60° C. for 5 hours and thencooled to room temperature. Thus, a hollow structural body of presentExample 1 was produced.

<Analysis>

The hollow structural body was cut into pieces measuring 10 mm×10 mm anda cut surface was observed by a scanning electron microscope (SEM). As aresult, it was a hollow structural body (see FIG. 2). The film thicknesswas about 1.0 μm.

Surface analysis of the structural body immediately after beingsubjected to a fluorination treatment and the hollow structural body wasconducted by using an X-ray photoelectron spectroscopy (XPS). As aresult, there was not a large difference in surface composition betweenboth structural bodies. It was also found that both structural bodieswere made of a fluorinated hydrocarbon polymer (see FIG. 3).Furthermore, a hollow ratio measured by the method described hereinafterwas 50%.

Example 2

First, a fluorination treatment was conducted in the same manner as inExample 1, except that a fibrous structural body 4 made of an olefinpolymer (Polypropylene SLFD 50125: manufactured by NKK).

Next, the structural body after being subjected to the fluorinationtreatment was cut into pieces measuring 20 mm×20 mm, followed byimmersion in 50 g of xylene (80%) at 110° C. for 24 hours. Next, thestructural body was taken out, washed with isopropyl alcohol, dried at90° C. for 5 hours and then cooled to room temperature. Thus, a hollowstructural body of present Example 2 was produced.

<Analysis>

The measurement of the thickness and surface analysis of the hollowstructural body were conducted in the same manner as in Example 1. As aresult, the film thickness was about 1.0 μm (see FIG. 4). It was alsofound that, regarding surface analysis, the surface composition of thestructural body immediately after being subjected to a fluorinationtreatment was almost the same as that of the hollow structural body, andthat both structural bodies were made of a fluorinated hydrocarbonpolymer (see FIG. 5). Furthermore, the hollow ratio measured by themethod described hereinafter was 60%.

Example 3

First, in the same manner as in Example 2, a fluorination treatment wasconducted. Next, the structural body was cut into pieces measuring 20mm×20 mm and heated to 300° C. in a nitrogen gas atmosphere at atemperature rise rate of 2.5° C./min. Furthermore, the structural bodywas fired in an electric furnace at 300° C. for 1 hour and then cooledto room temperature. Thus, a hollow structural body of present Example 3was produced.

<Analysis>

The measurement of the thickness and surface analysis of the hollowstructural body were conducted in the same manner as in Example 1. As aresult, the film thickness was about 1.0 μm (see FIG. 6). It was alsofound that, regarding surface analysis, the surface composition of thestructural body immediately after being subjected to a fluorinationtreatment was almost the same as that of the hollow structural body, andthat both structural bodies were made of a fluorinated hydrocarbonpolymer (see FIG. 7). Furthermore, the hollow ratio measured by themethod described hereinafter was 70%.

Example 4

A fluorination treatment was conducted in the same manner as in Example1, except that the structural body was retained at 30° C. for 1 hour ina state where a fluorine gas was allowed to continuously flow in thefluorination treatment, followed by heating to 90° C. at a temperaturerise rate of 0.3° C./min and further retention for 1 hour.

In the same manner as in Example 1, the structural body was immersed incyclooctane, then taken out, and washed with isopropyl alcohol anddried. Thus, a hollow structural body of present Example 4 was produced.

<Analysis>

The measurement of the thickness and surface analysis of the hollowstructural body were conducted in the same manner as in Example 1. As aresult, the film thickness of the hollow structural body produced inExample 4 was about 3.0 μm (see FIG. 8( a)). When compared with thehollow structural body produced in Example 1 (see FIG. 8( b)), thehollow structural body of the present Example had a hollow ratio ofabout 2/5. Furthermore, a hollow ratio of the hollow structural body ofthe present Example measured by the method described hereinafter was20%.

Example 5

A fluorination treatment was conducted in the same manner as in Example1, except that a fibrous structural body 4 made of polyester(manufactured by Asahi Kasei Corporation under the trade name of AsahiKasei ELTAS).

Next, the structural body was cut into pieces measuring 10 mm×10 mm andheated to 200° C. in a nitrogen gas atmosphere at a temperature riserate of 2.5° C./min. Furthermore, the structural body was fired in anelectric furnace at 200° C. for 6 hours and then cooled to roomtemperature. Thus, a hollow structural body of present Example 5 wasproduced.

<Analysis>

The measurement of the thickness and surface analysis of the hollowstructural body were conducted in the same manner as in Example 1. As aresult, the film thickness of the hollow structural body produced inExample 5 was about 1.0 μm (see FIG. 9). When compared with the hollowstructural body produced in Example 1, the hollow structural body of thepresent Example had the similar hollow ratio. It was also found that,regarding surface analysis, the surface composition of the structuralbody immediately after being subjected to a fluorination treatment wasalmost the same as that of the hollow structural body, and that bothstructural bodies were made of a fluorinated hydrocarbon polymer (seeFIG. 10). Furthermore, a hollow ratio measured by the method describedhereinafter was 50%.

(Measurement of Hollow Ratio)

A hollow ratio of the hollow structural body was measured in thefollowing manner. After taking a micrograph of a cross-sectional shapeof the hollow structural body by an electron microscope (magnification:×5,000), the micrograph was traced and the portion corresponding to theentire spun yarn including a hollow portion was cut, and then the mass(A) was measured. After the measurement, the portion corresponding tothe hollow portion was cut and the mass (B) was measured. This operationwas conducted with respect to 10 samples. Average values of A and B werecalculated and these values were substituted into the following equationto obtain a hollow ratio of the hollow structural body.

Hollow ratio (%)=(B/A)×100  [Equation 1]

What is claimed is:
 1. A hollow structural body, which has an openedhollow structural, prepared by a process comprising the steps of:providing a non-hollow structural body made of a hydrocarbon polymer,wherein said non-hollow structural body is formed from an outer surfaceand a center portion, wherein said hydrocarbon polymer forms said outersurface and said center portion, and wherein said hydrocarbon polymeroptionally has a nitrogen-containing group, a silicon-containing group,an oxygen-containing group, a phosphorus-containing group, or asulfur-containing group; bringing said non-hollow structural body intocontact with a treating gas containing fluorine under a predeterminedprocessing condition to allow the treating gas to permeate thestructural body from the outer surface toward the center portion and tofluorinate the structural body except for the center portion thereof;exposing the unfluorinated center portion after said fluorinationtreatment; and removing the exposed, unfluorinated center portion bydissolving or by the application of heat, thereby forming thefluorinated hollow structural body wherein in order to remove theunfluorinated center portion, the method includes one of the followingsteps: masking a portion of the exposed outer surface of the non-hollowstructural body before said fluorination treatment in order to preventfluorination at the masked portion due to said fluorination treatment,and subsequently removing said masking after said fluorinationtreatment, or cutting to expose unfluorinated center portion after saidfluorination treatment.
 2. The hollow structural body according to claim1, wherein a hollow ratio is within a range from 0.1 to 99%.